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<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        h1 {
            background-color: aqua;
            /* color: red; */
            /* color: rgb(0, 255, 0); */
            /* color: rgba(0, 0, 0,0.3); */
            color: #0000ff;
        }
    </style>
</head>
<body>
    <h1>h1 标签</h1>
</body>
</html>